Influence of environmental factors on spectral characteristics of chromophoric dissolved organic matter (CDOM) in Inner Mongolia Plateau, China

Z D Wen,Y Zhao,K S Song,J Du,J H Ma

doi:10.5194/hess-20-787-2016

Abstract

Abstract. Spectral characteristics of chromophoric dissolved organic matter (CDOM) were examined in conjunction with environmental factors in the waters of rivers and terminal lakes within the Hulun Buir plateau, northeast China. Dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorous (TP) were significantly higher in terminal lakes than rivers waters (p < 0.01). Principal component analysis (PCA) indicated that non-water light absorption and anthropogenic nutrient disturbances were the likely causes of the diversity of water quality parameters. CDOM absorption in river waters was significantly lower than terminal lakes. Analysis of the ratio of absorption at 250 to 365 nm (E250 : 365), specific ultraviolet (UV) absorbance (SUVA254), and the spectral slope ratio (Sr) indicated that CDOM in river waters had higher aromaticity, molecular weight, and vascular plant contribution than in terminal lakes. Furthermore, results showed that DOC concentration, CDOM light absorption, and the proportion of autochthonous sources of CDOM in plateau waters were all higher than in other freshwater rivers reported in the literature. The strong evapoconcentration, intense ultraviolet irradiance, and landscape features of the Hulun Buir plateau may be responsible for the above phenomenon. Redundancy analysis (RDA) indicated that the environmental variables total suspended matter (TSM), TN, and electrical conductivity (EC) had a strong correlation with light absorption characteristics, followed by total dissolved solid (TDS) and chlorophyll a. In most sampling locations, CDOM was the dominant non-water light-absorbing substance. Light absorption by non-algal particles often exceeded that by phytoplankton in the plateau waters. Study of these optical–physicochemical correlations is helpful in the evaluation of the potential influence of water quality factors on non-water light absorption in cold plateau water environments. The construction of a correlation between DOC concentration and water quality factors may help contribute to regional estimates of carbon sources and fate for catchment carbon budget assessments.

Highlights

Chromophoric dissolved organic matter (CDOM) is the colored component of dissolved organic matter (DOM) in the natural waters environment
Coefficients between environmental variables with axes in Redundancy analysis (RDA) indicated that total suspended matter (TSM), total nitrogen (TN), and electrical conductivity (EC) had a strong correlation with light absorption characteristics, followed by total dissolved solid (TDS) and chl a
There has been little knowledge of CDOM properties and their relationship to environmental factors in plateau areas based on previous research results

Summary

Introduction

Chromophoric dissolved organic matter (CDOM) is the colored component of dissolved organic matter (DOM) in the natural waters environment. Terrestrial allochthonous inputs are the dominant CDOM source in aquatic ecosystems (Nelson and Siegel, 2013; Zhou et al, 2015). Phytoplankton excretion, zooplankton, and bacterial metabolism are the major autochthonous CDOM sources (Coble, 2007). As an important constituent of DOM, which is the largest reservoir of organic carbon on Earth, CDOM plays a vital role in the global carbon cycle (Gonnelli et al, 2013; Mopper and Kieber, 2002). CDOM is one of the major light-absorbing constituents in natural waters; it can absorb solar radiation in the ultraviolet (UV) and visible ranges of the light spectrum to shield biota from harmful UV radiation.

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